"Fat taxes" would have to increase the price of unhealthy food and drinks by as much as 20% in order to cut consumption by enough to reduce obesity and other diet-related diseases, experts have said. Such levies should be accompanied by subsidies on healthy foods such as fruit and vegetables to help encourage a significant shift in dietary habits, according to research published in the British Medical Journal.

Academics led by Dr Oliver Mytton and Dr Mike Rayner of the Department of Public Health at Oxford University examined the evidence from around the world for what they call health-related food taxes. Denmark has brought in a "fat tax", Hungary a "junk food tax" and France a tax on all sweetened drinks. Peru intends to add levies to junk food and Ireland may also introduce such taxes. David Cameron last October said the UK should considering following suit.

While it is unclear how such taxes could be brought in and enforced, they could help ensure that poor diet plays less of a role in future in a range of illnesses such as heart disease, type two diabetes and tooth decay, as well as obesity.

Although the less well-off are affected more by health-related food taxes, they may also ultimately benefit because "progressive health gains are expected because poor people consume less healthy food and have a higher incidence of most diet-related diseases, notably cardiovascular disease", the authors say.

Evidence suggests that bigger health gains result from increasing the price of a broad range of foods rather than a narrow one, and sugary drinks offer the best proof that such a move can be effective. Research in America found that a 35% tax on drinks sweetened with sugar sold in a canteen, which added about 28p to the price, led to a 26% drop in sales. Studies have estimated that a 20% levy on such drinks in the US would cut obesity by 3.5% and that adding 17.5% to the cost of unhealthy food products in the UK could lead to 2,700 fewer deaths from heart disease.

But the food industry attacked the research. "When the whole of the food industry is focused on continuing to give hard-pressed families great tasting food at an affordable price, discussion of adding 20% to food prices seems fanciful if not irresponsible," said Terry Jones, director of communications for the Food and Drink Federation, which represents food producers and retailers. Firms were working with the Department of Health through its Public Health Responsibility Deal "to make meaningful improvements in public health through pledges in areas such as salt and calorie reduction, and our commitment to improving the health of our employees", he added.

Anne Milton, the public health minister, said the Department of Health was keeping an eye on all the evidence emerging internationally about such taxes. She defended the policy of relying on voluntary deals with food firms, which critics have criticised as an inadequate substitute for regulation of the food industry. "We are working with food companies through the Responsibility Deal to reduce calories and ensure healthier options are available. We believe that collective voluntary action can deliver real progress quickly," Milton added.